Vending machine and method for defrosting

ABSTRACT

A method includes sensing an exposure of a refrigerated compartment of a vending machine to ambient air and, in response, sensing an initial temperature of the refrigerated compartment. The method also includes, responsive to sensing the exposure to ambient air, selecting a procedure from a plurality of procedures according to the sensed initial temperature, and controlling a refrigeration system of the vending machine using the selected procedure during an initial period. The method may include sensing a current temperature of the vending machine and, once the refrigerated compartment reaches a second predetermined temperature, controlling the refrigeration system according to the sensed current temperature, monitoring an operational characteristic of a compressor of the refrigeration system, and performing a defrost procedure according to the monitored operational characteristic.

CROSS-REFERENCE TO RELATED APPLICATION AND CLAIM OF PRIORITY

The present application is related to U.S. Provisional Patent Application No. 61/195,160, filed Oct. 3, 2008, entitled “DEFROST STRATEGY”. Provisional Patent Application No. 61/195,160 is assigned to the assignee of the present application and is hereby incorporated by reference into the present application as if fully set forth herein. The present application hereby claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 61/195,160.

TECHNICAL FIELD OF THE INVENTION

The present application relates generally to refrigerated vending machines and, more specifically, to an apparatus and method for vending machine defrosting.

BACKGROUND OF THE INVENTION

During operation of a refrigeration system of a refrigerated vending machine, water vapor in the air may condense on the cooling elements (or coils) within the vending machine cabinet. Such condensation may freeze on the coils, and the resulting ice may inhibit the heat transfer from the cooling system to products contained within the vending machine. This reduced heat transfer may increase operating costs and decrease efficiency, and reduce product cooling. Moreover, if ice builds up within the unit, it may interfere with other components of the refrigeration system or vending machine and lead to mechanical failure.

Defrosting may be performed by temporarily removing all products from the vending machine cabinet, turning off power to the unit, leaving the doors to the unit open, and waiting for the ice to melt, and draining it appropriately. The defrosting process may be sped up by mechanical removal of ice, or by the introduction of gentle heat into the cabinet. For example, placing a pan of hot water in the vending machine and closing the vending machine may be an effective method. In addition, using a fan to blow room temperature air over the built-up ice may also speed up the melting process, as well as help to evaporate moisture from damp surfaces.

This process can be time consuming and labor intensive. Perishable products may require refrigeration during such a defrosting process. Determining when a defrost cycle is needed may require regular physical inspection of the machine.

SUMMARY

In one embodiment, a method includes sensing an exposure of a refrigerated compartment of a vending machine to ambient air. In response, the method further includes sensing an initial temperature of the refrigerated compartment, selecting a procedure from a plurality of procedures according to the sensed initial temperature, and controlling a refrigeration system of the vending machine using the selected procedure during an initial period.

In another embodiment, a vending machine includes a controller, a temperature probe, and a refrigeration system. The temperature probe and the refrigeration system are communicatively coupled to the controller. The controller senses an exposure of a refrigerated compartment of a vending machine to ambient air. In response, the controller also senses an initial temperature of the refrigerated compartment, selects a procedure from a plurality of procedures according to the sensed initial temperature, and controls a refrigeration system of the vending machine using the selected procedure during an initial period.

In yet another embodiment, a method includes sensing an opening of a door of a refrigerated compartment of a vending machine and, in response, sensing an initial temperature of the refrigerated compartment. The method also includes, in response to sensing the opening of the door and during an initial period, operating a compressor of a refrigeration system of the vending machine in cycles of activation and deactivation, where the compressor is activated and deactivated for predetermined lengths of time that are selected according to whether the initial temperature of the vending machine is above a predetermined temperature.

Before undertaking the DETAILED DESCRIPTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term “controller” means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts:

FIG. 1 illustrates a block diagram of a vending machine according to an embodiment of the disclosure;

FIG. 2 is a state diagram of initial refrigeration control of a vending machine according to an exemplary embodiment of the disclosure; and

FIG. 3 is a state diagram of refrigeration control for temperature maintenance and defrosting of a vending machine according to an exemplary embodiment of the disclosure.

DETAILED DESCRIPTION

FIGS. 1 through 3, discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged vending machine.

FIG. 1 illustrates a block diagram of a vending machine 100 according to an embodiment of the disclosure. The vending machine 100 includes a vending machine controller (VMC) 102 that operates to control functions of the vending machine 100. Such functions may include vending, payment, and refrigeration functions. In some embodiments, the control functions of the controller 102 may be implemented in a single microcontroller or microprocessor. In other embodiments, the control functions of the controller 102 may be distributed across a plurality of microcontrollers or microprocessors.

The vending machine includes a temperature probe 104 that is communicatively coupled to the VMC 102. The temperature probe 104 is located in a position within the vending machine 100 that enables the temperature probe 104 to sense a temperature that is representative of the temperature of products stored in the vending machine 100. For example, such a location may be in a product compartment of the vending machine 100 in which products are stored, or in a return air duct for air returning from the compartment to be chilled.

The vending machine 100 also includes a refrigeration system 106 that controls the temperature of the product compartment of the vending machine 100, in which products are stored. In the refrigeration system 106, a refrigerant is compressed in a compressor 108. The compressed refrigerant is cooled in condenser coils and then passes through an expansion device. The low pressure refrigerant flows through evaporator coils before returning to the compressor. An evaporator fan 110 pulls air from the product compartment over the evaporator coils and pushes chilled air back into the product compartment. The compressor 108 and the evaporator fan 110 are communicatively coupled to the VMC 102, which controls their operation. In some embodiments, the temperature probe 104 may be located in a position that that enables the temperature probe 104 to sense a temperature of the evaporator coils.

Typically, the product compartment of the vending machine 100 is accessible via a door for restocking products. The vending machine 100 further includes a door sensor communicatively coupled to the VMC 102. The door sensor 112 provides an indication of whether the door is open or closed.

The vending machine 100 also includes a cumulative clock 114 that is communicatively coupled to the VMC 102. The VMC 102 controls the cumulative clock 114 by resetting its value to zero, starting it without changing its value, stopping it, and reading its current value. The VMC 102 may use the cumulative clock 114 to determine a cumulative length of time that the compressor 108 has been activated by starting and stopping the cumulative clock 114 whenever the VMC 102 activates and deactivates, respectively, the compressor 108.

FIG. 2 illustrates a state diagram 200 of initial refrigeration control of a vending machine according to an exemplary embodiment of the disclosure. Often, the door that provides restocking access to the product compartment of the vending machine 100 comprises an entire sidewall of the compartment. As a result, a significant quantity of unchilled outside air may enter the compartment when the door is opened.

The introduction of outside air and unchilled products to the product compartment during restocking may cause the temperature within the compartment to rise. Furthermore, condensation may build up on products and surfaces inside the product compartment that are below the dew point. Similarly, when power is turned off to the vending machine 100, the refrigeration system 106 stops functioning and the temperature within the product compartment increases.

When the door is closed or the power is turned back on, the vending machine 100 enters an initial mode during which the VMC 102 operates the refrigeration system 106 to quickly bring the temperature within the product compartment to a desired operating temperature. This initial mode is illustrated in FIG. 2. From any state of the state diagram 200, when the door is opened, the VMC 102 enters a Door Open/Power Off state 202. Similarly, when power is first applied to the vending machine, the VMC 102 enters the Door Open/Power Off state 202.

When the door sensor 112 indicates that the door is closed, the VMC 102 moves from state 202 to either a Reload state 204 or an Initial Pulldown state 206, according to an initial temperature in the product compartment, as sensed by the temperature probe 104. If the initial temperature is less than 73 degrees Fahrenheit, the state of VMC 102 changes to the Reload state 204. If the initial temperature is greater than or equal to 73 degrees Fahrenheit, the state of VMC 102 changes to the Initial Pulldown state 206.

In both the Reload state 204 and the Initial Pulldown state 206, the VMC 102 controls the refrigeration system 106 according to scripted actions that include cycles of activating and deactivating the compressor 108, which are explained in more detail below. In either the Reload state 204 or the Initial Pulldown state 206, if the VMC 102 determines that the temperature probe 104 has reached a predetermined temperature set point, the state of the VMC 102 changes to a Steady State Temperature state 210.

In some embodiments, the predetermined temperature set point is 35 degress Fahrenheit. In other embodiments, the predetermined temperature set point is 37 degress Fahrenheit. While particular predetermined temperature set points have been described, it will be understood that in still other embodiments, other predetermined temperature set points may be utilized. In yet other embodiments, the predetermined temperature set point may be set by an operator of the vending machine 100.

If the VMC 102 completes the scripted actions in the Reload state 204 and the temperature probe 104 has not reached the predetermined temperature set point, then the state of the VMC 102 changes to a Reload Pulldown state 208. In the Reload Pulldown state 208, the VMC 102 again controls the refrigeration system 106 according to scripted actions, which are explained in more detail below. While in the Reload Pulldown state 208, if the VMC 102 determines that the temperature probe 104 has reached the predetermined temperature set point, the state of the VMC 102 changes to the Steady State Temperature state 210.

In the Reload State 204, the VMC 102 controls the refrigeration system 106 according to the following script of actions. As indicated above, if at any time during the performance of this script the VMC 102 determines that the temperature probe 104 has reached the predetermined temperature set point, the state of the VMC 102 changes to the Steady State Temperature state 210.

Reload state 204 Script:

-   -   1. Activate (turn on) the evaporator fan 110.     -   2. Wait two minutes.     -   3. Activate (start) the compressor 108.     -   4. Wait forty-five (45) minutes.     -   5. Deactivate (stop) the compressor 108. The evaporator fan 110         stays activated (running).     -   6. Wait three minutes.     -   7. Start the compressor 108.     -   8. Wait forty-five (45) minutes.     -   9. Stop the compressor 108. The evaporator fan 110 stays         running.     -   10. Wait two minutes.     -   11. Start the compressor 108.     -   12. Wait forty-five (45) minutes.     -   13. Stop the compressor 108. The evaporator fan 110 stays         running.     -   14. Wait two minutes.

Initial Pulldown state 206 Script:

-   -   1. Turn on the evaporator fan 110.     -   2. Activate (start) the compressor 108.     -   3. Wait FirstIPCompressorOnTime.     -   4. Deactivate (stop) the compressor 108. The evaporator fan 110         stays activated (running).     -   5. Wait four minutes.     -   6. Start the compressor 108.     -   7. Wait SecondIPCompressorOnTime.     -   8. Stop the compressor 108. The evaporator fan 110 stays         running.     -   9. Wait ten minutes.     -   10. Start the compressor 108.     -   11. Wait SecondIPCompressorOnTime.     -   12. Stop the compressor 108. The evaporator fan 110 stays         running. The evaporator fan 110 stays running.     -   13. Wait twenty minutes.

In some embodiments the FirstIPCompressorOnTime is 7 hours and the SecondIPCompressorOnTime is 6 hours. In other embodiments, which may be used with a smaller vending machine, the FirstIPCompressorOnTime and the SecondIPCompressorOnTime are both 5 hours.

Reload Pulldown state 208 Script:

-   -   1. Turn on the evaporator fan 110.     -   2. Activate (start) the compressor 108.     -   3. Wait RPCompressorOnTime.     -   4. Deactivate (stop) the compressor 108. The evaporator fan 110         stays activated (running).     -   5. Wait FirstRPCompressorOffTime.     -   6. Start the compressor 108.     -   7. Wait RPCompressorOnTime.     -   8. Stop the compressor 108. The evaporator fan 110 stays         running.     -   9. Wait SecondRPCompressorOffTime.     -   10. Start the compressor 108.     -   11. Wait RPCompressorOnTime.     -   12. Stop the compressor 108. The evaporator fan 110 stays         running.     -   13. Wait ThirdRPCompressorOffTime.

In some embodiments:

-   -   the RPCompressorOnTime is six hours,     -   the FirstRPCompressorOffTime is eight minutes,     -   the SecondRPCompressorOffTime is twelve minutes, and     -   the ThirdRPCompressorOffTime is twenty minutes.

In other embodiments, which may be used with a smaller vending machine:

-   -   the RPCompressorOnTime is five hours,     -   the FirstRPCompressorOffTime is twelve minutes,     -   the SecondRPCompressorOffTime is twelve minutes, and     -   the ThirdRPCompressorOffTime is twenty minutes.

While particular compressor on times and compressor off times for two embodiments have been described, it will be understood that in still other embodiments, other compressor on times and compressor off times may be utilized. While three compressor on-off cycles have been described for the two embodiments shown, it will be understood that more or fewer compressor on-off cycles may be used in any or all of the Reload state 204, the Initial Pulldown state 206, or the Reload Pulldown state 208.

FIG. 3 illustrates a state diagram 300 of the Steady State Temperature state 210, which provides refrigeration control for temperature maintenance and defrosting of a vending machine according to an exemplary embodiment of the disclosure. In some embodiments, while in the Steady State Temperature state 210, the VMC 102 maintains a temperature of the product compartment of the vending machine 100 within a range of temperatures. As described with reference to FIG. 3, the Steady State Temperature state 210 is entered when the temperature probe 104 has reached a predetermined temperature set point. Upon entering the Steady State Temperature state 210, the VMC 102 enters a state 302, deactivating the compressor 108, setting the cumulative clock 114 to zero, and leaving the evaporator fan 110 activated.

After two minutes, the VMC 102 enters a state 304. In the state 304, the temperature probe 104 is monitored and the compressor 108 is started and stopped according to the current temperature as sensed by the temperature probe 104. Specifically, when the compressor 108 is stopped and the temperature probe exceeds the predetermined temperature set point by a predetermined hysteresis amount, the compressor 108 and the cumulative clock 114 are started. In some embodiments, the hysteresis amount is 2.7 degrees Fahrenheit. When the compressor 108 is running and the temperature probe falls below the predetermined temperature set point, the compressor 108 and the cumulative clock 114 are stopped. In the state 302, the evaporator fan 110 is running both when the compressor 108 is activated and deactivated.

As described in the state 302, the predetermined temperature set point and the hysteresis amount define a range of temperatures where the temperature set point is at the low end of the range. In other embodiments, the VMC 102 may start the compressor 108 when the temperature probe 104 exceeds the temperature set point and stop the compressor 108 when the temperature probe falls below the temperature set point by more than the hysteresis amount. In such embodiments, the temperature set point is at the high end of the range of temperatures defined by the predetermined temperature set point and the hysteresis amount. In still other embodiments, the predetermined temperature set point and the hysteresis amount may be combined to define a range with the temperature set point in any desired position relative to the range. In still further embodiments, the hysteresis amount may be larger or smaller than 2.7 degrees Fahrenheit.

After thirty-six (36) hours, the VMC 102 enters a state 308. In the state 308, the temperature probe 104 is monitored and the evaporator fan 110 is started and stopped along with the compressor 108, according to the current temperature as sensed by the temperature probe 104. Control of the compressor 108 and the cumulative clock 114 according to the current value of the temperature probe 104 is the same as that described for the state 304.

In either the state 304 or the state 308, if a predetermined defrost trigger is reached, the VMC 102 will enter a state 306 or a state 310, respectively. In both the state 306 and the state 310, the VMC 102 performs a defrost function by turning off the compressor 108, while leaving the evaporator fan 110 running. After fifteen minutes, the VMC 102 returns from the state 306 to the state 304, or from the state 310 to the state 308.

In some embodiments, the defrost trigger is a total accumulated time that the compressor 108 has been activated since a last previous defrost cycle or since last entering the Steady State Temperature state 210. While in the state 304 or the state 306, the VMC 102 starts and stops the cumulative clock 114 when starting and stopping, respectively, the compressor 108. When the length of time measured by the cumulative clock 114 exceeds 180 minutes, the defrost trigger is reached and either the state 306 or the state 310 is entered to perform a defrost cycle. When the defrost cycle is completed, the VMC 102 resets the cumulative clock 114 to zero, returns to the state 304 or the state 306, and resumes starting and stopping the cumulative clock 114 when starting and stopping, respectively, the compressor 108.

In other embodiments, the defrost trigger is a number of activations of the compressor 108 since a last previous defrost cycle or since last entering the Reload state 204. While in the state 304 or the state 306, the VMC 102 increments a counter each time the compressor 108 is started. When the counter value reaches 20, the defrost trigger is reached and either the state 306 or the state 310 is entered to perform a defrost cycle. When the defrost cycle is completed, the VMC 102 resets the counter to zero, returns to the state 304 or the state 306, and resumes counting activations of the compressor 108.

In still other embodiments, both the total accumulated time that the compressor 108 has been activated and the number of activations of the compressor 108 are monitored. The defrost trigger may be reached when the first of 180 minutes of activation or 20 activations is reached, and a defrost cycle performed. When the defrost cycle is completed, both the cumulative clock 114 and the activation counter are reset to zero.

It the embodiment described with reference to FIG. 2 and FIG. 3, the cumulative clock 114 tallies only time that the compressor 108 is activated while in the Maintain Temperature mode 210. In another embodiment, the cumulative clock 114 also tallies time that the compressor 108 is activated while in one or more of the Reload state 204, the Initial Pulldown state 206, or the Reload Pulldown state 208. In such an embodiment, the cumulative clock 114 is reset to zero each time the compressor 108 is stopped when the temperature probe 104 is above the predetermined temperature set point. When the compressor 108 is started, the cumulative clock 114 is started. Thus, if the temperature probe 104 reaches the predetermined temperature set point VMC 102 and changes to the Maintain Temperature mode 210, any final period that the compressor 108 was running will be included in the total time count accumulated by the cumulative clock 114.

Although the present disclosure has been described with an exemplary embodiment, various changes and modifications may be suggested to one skilled in the art. It is intended that the present disclosure encompass such changes and modifications as fall within the scope of the appended claims. For example, while temperatures have been expressed in Fahrenheit in this disclosure, it will be understood that in other embodiments temperature measurements may be made in Centigrade or another suitable temperature scale. 

1. A method, comprising: sensing an exposure of a refrigerated compartment of a vending machine to outside air; and responsive to sensing the exposure of a refrigerated compartment to outside air, sensing an initial temperature of the refrigerated compartment, according to the sensed initial temperature, selecting a procedure from a plurality of procedures, and controlling a refrigeration system of the vending machine using the selected procedure during an initial period.
 2. The method of claim 1, wherein the step of sensing an exposure of a refrigerated compartment of a vending machine to ambient air comprises sensing an opening of a door of the refrigerated compartment.
 3. The method of claim 1, wherein the procedure is selected according to whether the initial temperature of the vending machine is above a first predetermined temperature.
 4. The method of claim 1, wherein the step of controlling the refrigeration system during the initial period further comprises: activating a compressor of the refrigeration system for a first predetermined length of time; and deactivating the compressor for a second predetermined length of time, where the first and second predetermined lengths of time are selected according to the sensed initial temperature.
 5. The method of claim 1, further comprising: sensing a current temperature of the vending machine; and during a second period: controlling the refrigeration system according to the sensed current temperature, monitoring an operational characteristic of a compressor of the refrigeration system, and performing a defrost procedure according to the monitored operational characteristic.
 6. The method of claim 5, wherein the defrost procedure is performed according to one of an accumulated length of time the compressor has been activated and a number of activations of the compressor.
 7. The method of claim 5, wherein the second period begins when a second predetermined temperature of the vending machine is sensed.
 8. The method of claim 7, wherein the step of controlling a refrigeration system according to the sensed current temperature further comprises activating an evaporator fan of the refrigeration system for a third predetermined length of time after the temperature of the vending machine reaches the second predetermined temperature.
 9. The method of claim 8, wherein the step of controlling a refrigeration system according to the sensed current temperature further comprises, after the third predetermined length of time, deactivating the evaporator fan when the compressor is deactivated.
 10. A vending machine, comprising: a controller; a temperature probe communicatively coupled to the controller; and a refrigeration system communicatively coupled to the controller, wherein the controller is adapted to: sense an exposure of a refrigerated compartment of a vending machine to outside air; and responsive to sensing the exposure of a refrigerated compartment to outside air, sense an initial temperature of the refrigerated compartment, according to the sensed initial temperature, select a procedure from a plurality of procedures, and control a refrigeration system of the vending machine using the selected procedure during an initial period.
 11. The vending machine of claim 10, wherein the controller is further adapted to select the procedure according to whether the initial temperature of the vending machine is above a first predetermined temperature.
 12. The vending machine of claim 10, wherein the controller is further adapted to, during the initial period: activate a compressor of the refrigeration system for a first predetermined length of time; deactivate the compressor for a second predetermined length of time; and select the first and second predetermined lengths of time according to the sensed initial temperature.
 13. The vending machine of claim 10, wherein the controller is further adapted to: sense a current temperature of the vending machine; and during a second period: control the refrigeration system according to the sensed current temperature, monitor an operational characteristic of a compressor of the refrigeration system, and perform a defrost procedure according to the monitored operational characteristic.
 14. The vending machine of claim 13, wherein the controller is further adapted to perform the defrost procedure according to one of an accumulated length of time the compressor has been activated and a number of activations of the compressor.
 15. The vending machine of claim 13, wherein the controller is further adapted to begin the second period when a second predetermined temperature of the vending machine is sensed.
 16. The vending machine of claim 15, wherein the controller is further adapted to, when the second period begins, activate an evaporator fan of the refrigeration system for a third predetermined length of time.
 17. The vending machine of claim 16, wherein the controller is further adapted to, during the second period, after the third predetermined length of time, deactivate the evaporator fan when the compressor is deactivated.
 18. A method, comprising: sensing an opening of a door of a refrigerated compartment of a vending machine; and responsive to sensing the opening of the door, sensing an initial temperature of the refrigerated compartment, and during an initial period, operating a compressor of a refrigeration system of the vending machine in a plurality of cycles of activation and deactivation, where the compressor is activated and deactivated for predetermined lengths of time selected according to whether the initial temperature of the vending machine is above a first predetermined temperature.
 19. The method of claim 18, further comprising: sensing a current temperature of the vending machine; and during a second period that begins when a second predetermined temperature of the vending machine is sensed: controlling the refrigeration system according to the sensed current temperature, monitoring an operational characteristic of a compressor of the refrigeration system, and performing a defrost procedure according to the monitored operational characteristic.
 20. The method of claim 19, wherein the defrost procedure is performed according to one of an accumulated length of time the compressor has been activated and a number of activations of the compressor.
 21. The method of claim 19, wherein the step of controlling the refrigeration system according to a sensed current temperature further comprises: activating an evaporator fan of the refrigeration system for a predetermined length of time after the second predetermined temperature is sensed; and subsequently, activating the evaporator fan when the compressor is activated and deactivating the fan when the compressor is deactivated. 